Recorder apparatus



April 23, 1940. O s PETERS 2,198,040

RECORDER APPARATUS Filed July 2'7, 1935 INVENTOR TTORNE Patented Apr. 23, 1940 UNITED STATES PATENT OFFld g 2,198,040 RECORDER APPARATUS Application July 27, 1935, Serial No. 33,469

6 Claims.

This invention relates to a recorder for graphically recording the relation of stress and strain of a specimen under test in a materials testing machine and relates more particularly to improved means for recording strain of a specimen during either loading or unloading thereof.

It has heretofore been proposed to record strain during loading and unloading of a specimen; but this has been accomplished by mecha-v l0 nism whose characteristics during loading are adapted for indicating both increases and decreases in strain and similarly during unloading the characteristics are adapted to be responsive to both increases and-decreases in strain. As a result, the graphic representation on the recorder chart is in the nature of a relatively wide line or band. Such-a wide band is sometimes diflicult of accurate interpretation of the stress or strain characteristics of the specimen. Other devices have heretofore been proposed such as shown in the joint invention of myself and G. S. von Heydekampf, Patent No. 2,081,598, wherein during increases of strain the graphic representation thereof is a very narrow line or band, thus 25 permitting a very accurate interpretation of the stress and strain characteristics of the specimen. This arrangement, however, is .limited merely to recording increases in strain.

It is an object of my invention to provide an improved means whereby a relatively narrow line records the stress and strain during increasesor decreases thereof such as is usually brought about by loading and unloading of the specimen. Such loading and unloading operation is usually em- 35 ployed in making a hysteresis test. It is a further object of my invention to accomplish the foregoing result without having the mechanism encumber the record during the increase of strain with mechanical characteristics that are prefer- 40 ably useful only with decrease of strain, or vice versa. A still further object is to provide improved means whereby at very critical points in the stress-strain relation, where. it may be diflicult to determine whether the strain is increas- 45 ing or decreasing, the operator may simultaneously employ both the strain increasing and decreasing responsive characteristics of the mech anism, but that after such a critical point has been passed he may eliminate one or the other ing description of the accompanying drawing in 65 which:

of the characteristics of the'mechanism so that a Fig. 1 is a diagrammatic plan view of the apparatus showing the parts in their cooperative relation; I

Fig. 2 is an enlarged plan view of an electrical follow-up device part of which is broken away in ii show the details of construction.

Fig. 3 illustrates three forms of curves obtainable with my improved apparatus.

In the particular embodiment of the invention which is shown herein merely for the purpose of 10 illustrating one specific form among possible others that the invention might take in practice,

I have shown the invention as applied to a materials testing machine of. the hydraulic type. Such a machine is merely a diagrammatic repre- 1 sentation of one of the various types of materials testing machines with which my invention may be employed as will be 'apparent to those skilled in the art.

Referring to the drawing in detail, an electric 20 motor I drives a shaft 2 through reducing gears 3 and 6. On the shaft 2 are secured worms '5 and 8 for operating worm gears 5 and 6, to the shafts of which are secured bevel gears 9 and It. Thus with the motor 8 continuously in operation, 5 bevel gears 9 and I0 are continuously in rotation, the object being to supply power to the recording devices when required.

One form of materials testing machine, to be described more fully hereinafter, is diagrammati- 3o cally shown as having a piston ll arranged to slide in a hydraulic chamber l2 within which the pressure may be varied by means of a pump it, fluid therefrom being supplied to chamber I? through the pipe It. From the chamber l2 8. tube l5 leads to a pressure gage mechanism iii of the Bourdon tube type, whose shaft 11 has a hand I8 which rotates as the pressure within the Bourdon tube It changes. The hand l8 carries at its outer end a screw 20 with a metal whisker 2| aflixed thereto. v

The whisker M in its normal position rests. without touching within a gap 22 in a segmental metal ring consisting of two segments 23 and 2d separated by gaps 22 and 22', but is so constructg ed that in the event of a sudden movement of the hand l8 it can ride up on either segment 23 or 2d. The segments 23 and 2d are secured to and are coaxial with a disk of insulating mate-- rial 25, and are also coaxial with the axis of rota- 56 tion of hand l8 so that whisker 2! is in contact 7 with either segment 23 or 24 at all parts of its travel except while in the gap ,22 or in the corresponding gap at the opposite end of segment 2 3. Disk 25 carries on its back two continuous metal 5 rings 26 and 21, arranged concentrically and secured to the disk 25 so as to rotate with it. Ring 26 is connected electrically to segment 24, and

ring 21 to segment 23. In contact with the rings 26 and 21 are two metallic brushes 28 and 29 which lead to the coils of a double acting solenoid 36. The armature 3| of the solenoid is secured to a lever 32 secured to a yoke 46 for oscillating the same about a center 33. Yoke 46 carries in bearings 34 and 35 a shaft 36 upon which are mounted bevel gears 31 and 38 adapted when alternatively engaged with the bevel gear |6'to be rotated thereby in one direction or the other, depending upon which gear is engaged.

Mounted upon shaft 36 is spiral gear 39 engaging a spiral gear 46 whose shaft 4| has a worm 42 meshing with a worm wheel 43, which in turn is secured upon the shaft of the disk 25 and rotates therewith.

The operation of this portion of the apparatus which records the load or stress coordinate, represented by the pressure, is as follows: A pressure change in the chamber I2 is accompanied by a rotation of the hand |8 which brings the whisker 2| in electrical contact with either segment 23 or 24, depending upon whether the pressure change is an increase or a decrease. This operation energizes the corresponding side of solenoid 36 through the medium of the battery 44 which is connected to the mid-point of the solenoid winding and to the frame of the pressure gage |6 at 45. When one side of the solenoid 36 is energized, the armature is drawn in, and through lever 32 and yoke 46, which rotates about center 33. bevel gear 31 is engaged with bevel gear l6. The rotation of bevel gear I6 is thereby transmitted through the medium of spiral gears 39 and 46, worm 42 and worm gear 43 to the disk 25, which thereby tends to rotate in the same direction as hand l8 and break the contact between the whisker 2| and segment 23 or 24. This break in contact releases solenoid 36 and causes bevel gear |6 to become disengaged. As the pressure in chamber l2 increases or decreases, the hand l6 and disk 25 will rotate together with a degree of hunting which may be controlled by the width of the gap 22.

On increasing pressure, the hand I8 is preferably made to rotate in a counter-clockwise direction, or towards segment 23, which is made less than one-fourth of the total circumference of rotation of hand I8. Segment 24 is correspondingly made greater than three-fourths of the circumference. The reason for this is that, as commonly, constructed, Bourdon tube type pressure gages show a rotation of three-fourths of a complete circle on full pressure. Thus if hand I8 is rotated to three-fourths of a circle and the pressure is suddenly released, the return rotation does not carry whisker 2| beyond segment 24,, but remains in contact with it to energize solenoid 36 on the opposite side to cause gears 6 and 38 to mesh to bring the disk 25 back to its initial position.

At the back of disk 25 is affixed a pulley 41. One end of a cord 48 is attached to pulley 41 and passes around a pulley 49 and over a groove in a rotatable drum 56 to a weight 5| which is suspended under the action of gravity. Since the cord 48 is under constant tension from the weight 5|, it places disk 25 and drum 56 in exact rotational relation with each other. Thus as disk 25 follows hand |8 in direct relation to the pressure in chamber l2, itdraws drum 56 with it in exact rotational relation therewith through the medium of the cord 48. If a sheet of paper 62 be amxed to the drum, and a pencil 53 be aflixed to the pencil carriage 15 with its point resting on the paper 52, a line will be drawn on the paper which in length circumferentially to the drum 56 will be in direct ratio to the pressure in the chamber I2.

As the pressure changes, more or less force is exerted on the piston II and thence transmitted through a movable frame 55 to a specimen 56, which is aflixed at its ends to the frame 55 and to the stationary frame 51.

The application of force to the specimen 56 causes it to elongate in accordance with wellknown physical laws. A sharp metallic point 58 fixed in frame 59 is forced into the specimen 56 and engaged therewith by means of a clamp 66. A sharp metallic point 6| fixed in block 62 is likewise forced into the specimen and engaged therewith by the clamp 66. The clock 62 and frame 59 are rotatably engaged by means of trunnions 63. -To block 62 is aflixed an arm 64 which carries at its outer end an insulated electrical contact point 65. At the upper end of the frame 59 is mounted a micrometer screw head 66 in an insulating bushing 61, and carrying on its rotatable sleeve a fixed pulley 68. At the inner end of the head 66 is mounted a second electrical contact point 69 axially in line with the contact 65.

A weight 16 is attached to a cord 1| to maintain the cord at constant tension over the pulley 68 and around pulleys 12, 18 and 14. The end of the cord 1| is attached to a pencil carriage 15 which is movable longitudinally upon rod 54.

From contacts 65 and 69 insulated wires lead to a battery 16 and a relay 11, which, when energized, opens a contact 18 assuming that a manually operable swltch 18' is closed. Contact 18 when closed is in series with a battery 19, solenoid 86 and switch 18'. The armature of solenoid 86 is afiixed to a lever 8| of a yoke 82 which is rotatable about a center 83. Carried in bearings 84 and 85 is a shaft 86 to the ends of which are afflxed bevel gears 81 and 88. Shaft 86 carries a spiral gear 89 meshing with a spiral gear 96 whose shaft has a worm 9| for driving a worm gear 92. The shaft of worm gear 92 carries pulley 93.

Arm 8| is provided with a lateral projection serving as a core for a solenoid 86 in the same manner as solenoid 86. Energization of solenoid 86' swings yoke 82 in a counterclockwise direction to cause engagement between bevel gears 9 and 86. Solenoid 86'. is connected to one side of battery 19 and to the other side thereof through a manually operable switch 18" and a contact 18a adapted to be closed upon energization of relay 11. Gears 9 and 88 or gears 9 and 81 may be thrown out of mesh merely by coaction between the teeth upon deenergization of solenoids 86 and 86' although if desired arm 8| and the gear yoke 82 may be yieldably held in their neutral position by a pair of opposed springs 8| and 8|".

An endless cord 94 passes around the pulley 93, and also around pulleys 95, 96, 91, 98, 99 and |66 to pencil carriage 15, to which it is aflixed so that if the cord moves the pencil carriage moves with it by sliding on rod 54, about which rod the pencil rotates so the point of pencil 53 may rest on paper 52.

The operation of this portion of the apparatus is as follows: Assuming switch 16' to be closed and switch 18" to be open, then as pressure in the chamber |2 increases. piston moves up- 15 ward increasing the separation between frames 55 and 51 and applying force to the specimen 56 which elongates, a portion of the elongation taking place between the points 58 and GI. The result of this elongation is to rotate the block 62 and arm 64 counterclockwise in trunnions 63 and thus separate contacts 65 and 69. As the electrical circuit is thus broken, relay II is deenergized permitting contact I8 to close and energize solenoid from battery I9. The armature of solenoid 86 is thus drawn in, rotating yoke 82 clockwise through lever 8| around the axis oi shaft 83 and engaging gears 9 and 81 which, through the medium of spiral gears 89 and 90 and worm 9| and worm gear '92, causes pulley 93 to rotate and move the pencil carriage 15 through the medium of cord 94. As the pencil carriage I5 moves, it carries with it the cord H which rotates the pulley 68 and causes the micrometer screw head 66 to advance and close contacts 65 and 69. As this occurs, relay TI is energized, opening contact 18 and releasing solenoid 80 which permits gears 9 and 81 to become disengaged, thus stopping the pencil carriage I5.-

Thus as the elongation between points 58 and 6| proceeds, the contacts 65 and 69 are alternately separated and closed and the pencil carriage I5 is moved in steps in a direction parallel to the axis of the drum by an amount which bears a direct relation to the elongation in specimen 56 in the portion between points 58 and 6|.

.The pressure change in chamber I2 which acts to produce this elongation. is communicated to drum 56 in the manner described heretofore, causing drum 50 to rotate proportionally, thus combining the two motions to draw a single line IN, the coordinates of which circumferentially to the drum are proportional to the pressure, and longitudinally are proportional to the elongation in specimen 56 between the points 58 and 65.

By proper mechanical refinements, the steps in both directions are reduced to such small amounts for each period of operation of the device that the resultant appears to be a smooth curve. The smoothness of operation is greatly enhanced by arranging the circuits and mechanism so the power from the motor I tends to raise the weights 5! and I6 against the action of gravity with increasing pressure in chamber l2 and increasing elongation in specimen 58.

The foregoing operation has reference to increases in strain which are usually accompanied by an increase in load. If it is desired to produce a record of the strain characteristics while decreasing the load, then switch I8 is opened and switch 18" closed in which event contraction of the specimen between points 58 and 6! will cause contacts 65 and 69 to close, thereby energizing solenoid TI and closing contacts 18a, whereupon current from battery I9 will energize solenoid 80' and thus engagebevel gears 9 and 88. Cord 96 will immediately be driven in a reverse direction so as to move pencil carriage I5 in such manner as to indicate a decrease in strain. Upon movement of carriage I5, cord Ii will be reversely actuated thereby reversely rotating micrometer screw 66 and thus open contacts 65 and 69. Solenoid Ti will thereupon be deenergized to open contacts 18a, resulting in deenergization of solenoid 88' and return of block 82 to its neutral position with disengagement of bevel gears 9 and 88. However, in practical operation, the opening of contacts 65 and 69 is accompanied by a stilland thus repeating the operation just described. The length of time .that gears 9 and 68 remain in mesh will of course depend upon the rate at which the strain of the specimen decreases. The motor I and shaft 2 are of course rotated at a speed in excess of that required for the largest possible rate of change of strain of a specimen, Hence it is seen that engagement of gears 8 and 88 is-only an intermittent operation.

In' running atest for strain during loading, switch I8 is closed and switch 18" opened, thereby producing a curve as indicated at I00 in Fig. 3A. If it is desired to record strain characteristics upon unloading or decreases in strain, then whenthe curve. approaches the knee I68, the operator closes switch 18" and opens switch 18', thereby, producing the reduced strain curve l8l. It'will be noted that in each case the width of the lines is determined by the increments of movement of carriage I5, which movements will be proportional to the fineness of the teeth between the bevel gears 9 and 88 or 9 and 81; This produces a line or band that is relatively narrow, thus permitting accurate interpretations of the strain characteristics on the chart. However, should it be desired to avoid manual manipulation of switches I8 and 18" at the critical point near the knee I62 01' the curve, Fig. 3-B, the operatormay close both of said switches at a point just before the knee is reached. The result ofthis operation is that solenoids 88 and 88' are alternately electrically energized to give opposite electrical effects with the result that pencil carriage I5 is given a slight reciprocating action of twice the magnitude that it would have with only one solenoid 80 or 88 adapted to be energized. This operation, however, has the advantage that the complete knee of the curve is attained automatically without guesswork on the part of the operator. When the operator observes that the knee of the curve has been passed he may then disconnect switch I8 and thereby obtain a substantially' fine line graph of the reducing strain characteristics of the specimen. If desired, the operator can close both switches I8 and 18" throughout the complete up and down range of the curves, although this would involve sacrifice in accurately interpreting the curves such as is shown at I03, Fig. 3-C.

For a complete understanding of the invention, I have disclosed a preferred modification thereof. It is to be understood, however, that variations and equivalents are contemplated such as will be embraced within the scope of the claims which follow.

I claim:

1. Apparatus for recording physical characteristics of a test specimen stressed in a materials testing machine comprising, in combination, a chart and marker, continuously rotating power operated means, and mechanism adapted to be operated thereby for effecting reversible relative movement between the chart and marker in accordance with increases and decreases in strain including control means responsive only to increases of strain and control means responsive only to decreases in strain.

2. Apparatus for recording physical characteristics of a test specimen stressed in a materials tesfing machine comprising, in combination, a chart and marker, continuously rotating power operated means, mechanism adapted to be operated thereby for effecting reversible relative movement between said marker and chart in accordance with increases and decreases in strain,

and means for controlling said mechanism so that it is selectively responsive either to only increases or only decreases in strain or to both.

3. Apparatus for recording physical characteristics of a test specimen stressed in a materials testing machine comprising, in combination, a chart and marker, continuously rotating power operated means, and mechanism adapted to be operated thereby for effecting reversible relative 30 movement between said marker and chart in accordance with increases and decreases in strain including electric means responsive to increases in strain and other electric means responsive to decreases in strain of the specimen. a 4. Apparatus for recording physical characteristics of a test specimen stressed in a materials testing machine comprising, in combination, a chart and marker, continuously rotating power operated means, and mechanism adapted to be 20 operated thereby for eflecting reversible relative movement between said marker and chart in accordance with increases and decreases in strain including electric means responsive to increases in, strain and other electric means operating in as opposed relation to said first electric means and responsive to decreases in strain of the specimen.

5. Apparatus for recording physical characteristics of a test specimen stressed in a materials testing machine comprising, in combination, a

chart and marker, continuously rotating power operated means, and mechanism adapted to be operated by said power means for eiiecting relative movement between said marker and chart in accordance with strain variations including con- 5 trol means having electrical eifects in opposed relation to each other and responsive to strainvariations; said control means having a pair of solenoids and means common to each of said solenoids for eflective alternative energization 1 thereof.

6. Apparatus for recording physical characteristics of a test specimen stressed in a materials testing machine comprising, in combination, a chart and marker, continuously rotating power 15 operated means, and mechanism adapted to be operated by said power means for eii'ecting relative movement between said marker and chart in accordance with strain variations including control means having electrical eil'ects in opposed relation to each other and responsive to strain variations; said control means having a pair of solenoids and an armature therefor, means common to each of said solenoids for eflecting alternative energization thereofiand means for re- 25 storing the armature of said solenoids to a neutral position upon deenergization thereof.

ORV-[LIE S. PETERS. 

